Larger and evermore complex battery systems composed of many individual cells are being constructed to provide larger voltages and powers, such as used in electric and hybrid vehicles, backup stationary power for computing centers, homes and whole neighborhoods. Dividing the battery into packs of smaller groups of cells can be advantageous to assembly, safety, servicing and maintenance. However, large battery systems composed of one or many cells in parallel (a module), then connected in series configurations for higher voltages, typically are limited by the weakest module and/or cell in the amount of current that the battery system can supply. Battery management systems have been developed to balance these modules so they remain as close to equal charge as possible to provide the best performance. As these batteries are constructed with larger voltages, it is recommended to break the battery into separated lower voltage packs connected in series, so each pack works at reduced voltages, allowing lower cost and often fewer components to be used in the construction. Active balancing is more efficient than passive load balancing of cells in maintaining optimal battery condition.